In recent years, there is an increasing demand for energy saving in residential spaces of houses, offices, and the like, and building materials used for houses and the like are also required to contribute to energy saving. Generally, attempts have been made to increase the cooling/heating efficiency by using a heat insulation material for the floor, ceiling, wall surface, or the like. However, for further energy saving, various materials have been studied. In addition, similarly, there also is a high demand for energy saving in closed spaces of automobiles, aircrafts, and the like, and the inside of refrigerators of refrigerator cars and the like.
As such a material, for example, a material obtained by mixing an encapsulated latent heat storage medium with a gypsum board is disclosed (see PTL 1). In addition, as a material using a flexible material, for example, a heat-storing thermoplastic resin sheet containing a heat storage medium in a thermoplastic resin is disclosed (see PTL 2).